The glypican family has been reported to be present as a new family of heparan sulfate proteoglycans that are present on cell surfaces. To date, the 5 types of glypicans (glypican 1, glypican 2, glypican 3, glypican 4 and glypican 5) have been reported as members of the glypican family. These members of the family have a core protein of uniform size (approximately 60 kDa), share specific and well-conserved cysteine sequences, and bind to cell membranes via glycosyl phosphatidyl inositol (GPI) anchors.
Glypican 3 (GPC3) has been known to be involved in cell division, or the control of cell division pattern during development, and that a GPC3 gene is highly expressed in hepatic cancer cells. Accordingly, the GPC3 gene may be used as a hepatoma marker.
We have previously found that an anti-GPC3 antibody has ADCC activity and CDC activity, and is useful for the therapy of hepatic cancer, and have applied for a patent (Japanese Patent Application No. 2001-189443).
GPC3 is a membrane-bound protein. It has not been reported that a secretory type GPC3 is present in blood and that the GPC3 protein can be used as a cancer marker.